In the process of establishing an oil or gas well, the well is typically provided with an arrangement for selectively excluding fluid communication with certain zones in the formation to avoid communication with undesirable fluids. A typical method of controlling the zones with which the well is in fluid communication is by running well casing down into the well and then sealing the annulus between the exterior of the casing and the walls of the wellbore with cement. Thereafter, the well casing and cement may be perforated at preselected locations by a perforating device or the like to establish a plurality of fluid flow paths between the pipe and the product bearing zones in the formation. Unfortunately, the process of perforating through the casing and then through the layer of cement dissipates a substantial portion of the energy from the perforating device and the formation receives only a minor portion of the perforating energy.
Perforating in wellbores is typically accomplished by the use of perforating guns which usually employ shaped charges or bullets. The guns are usually positioned in the wellbore on a tubing string or suspended from a cable. Detonating the explosive in the gun is sometimes accomplished by initiating a detonating cord which is positioned adjacent a shaped charge. Various electrical, hydraulic and mechanical systems are employed to initiate the detonating cord. The detonating systems which are now used in this industry have many safety drawbacks especially when electrical energy is used to initiate the process. Accordingly, it is an object of the present invention to provide a new and improved system to initiate an explosive device.
It is a further object to provide a system to safely initiate an explosive device at a remote location as, for example, in a wellbore.
Additionally, it is an object of the present invention to provide a method and apparatus for perforating a wellbore which overcomes or avoids the above noted limitations and disadvantages of the prior art.
It is yet another object of the present invention to provide a method and apparatus for detonating explosive charges by a pressure wave or pulse.